Wireless communication system

ABSTRACT

A wireless communication system includes a first communication apparatus including a first antenna and a second antenna, a second communication apparatus including a third antenna and a fourth antenna, a first communication control unit that controls wireless communication based on electric field coupling or magnetic field coupling between the first antenna and the third antenna, and a second communication control unit that controls wireless communication based on electric field coupling or magnetic field coupling between the second antenna and the fourth antenna.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/865,112, filed on Jan. 8, 2018, which claims priority fromJapanese Patent Application No. 2017-002712, filed Jan. 11, 2017, andNo. 2017-225480, filed Nov. 24, 2017, which is hereby incorporated byreference herein in its entirety.

BACKGROUND Field of the Invention

The present disclosure relates to a wireless communication system.

Description of the Related Art

In recent years, there has been proposed a near-field wirelesscommunication system carrying out communication based on electromagneticfield coupling between a pair of antennas placed in proximity to eachother. Japanese Patent Application Laid-Open No. 2009-268022 discusses amethod for transmitting an electric signal without modulating it basedon the baseband method in the wireless communication based on theelectromagnetic field coupling, thereby realizing high-speed andlow-delay communication with a simple circuit configuration.

However, in recent years, a data amount to be communicated has beenincreasing, and realization of further high-speed communication in thewireless communication system has been demanded.

SUMMARY

According to an aspect of the present disclosure, a wirelesscommunication system includes a first communication apparatus includinga first antenna and a second antenna, a second communication apparatusincluding a third antenna and a fourth antenna, a first communicationcontrol unit configured to control wireless communication based onelectric field coupling or magnetic field coupling between the firstantenna and the third antenna, and a second communication control unitconfigured to control wireless communication based on electric fieldcoupling or magnetic field coupling between the second antenna and thefourth antenna. The first antenna, the second antenna, the thirdantenna, and the fourth antenna are positioned such that an electricsignal transmitted from the first antenna and received by the secondantenna is weaker in strength than a strength of an electric signaltransmitted from the first antenna and received by the third antenna.

Further features will become apparent from the following description ofexemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system configuration of awireless communication system 100.

FIGS. 2A and 2B illustrate a configuration example of couplers in thewireless communication system 100.

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F illustrate electric signalscommunicated in the wireless communication system 100.

FIG. 4 illustrates a system configuration of a wireless communicationsystem 400.

FIG. 5 is a block diagram illustrating a system configuration of awireless communication system 500.

FIG. 6 is a block diagram illustrating a system configuration of awireless communication system 600.

FIGS. 7A, 7B, 7C, 7D, 7E, and 7F illustrate interference of the electricsignals communicated in the wireless communication system 100.

FIGS. 8A and 8B illustrate a configuration example of the wirelesscommunication system 100 for preventing or reducing the interference ofthe electric signals.

FIGS. 9A, 9B, 9C, and 9D illustrate a configuration example of thewireless communication system 100 for preventing or reducing theinterference of the electric signals.

FIGS. 10A and 10B illustrate a configuration example of the wirelesscommunication system 100 including parallelly movable couplers.

FIGS. 11A, 11B, and 11C illustrate a configuration example of thewireless communication system 100 including rotatably movable couplers.

FIGS. 12A, 12B, and 12C illustrate examples of structures of thecouplers.

FIGS. 13A, 13B, and 13C illustrate a configuration example of thewireless communication system 100 for preventing or reducing theinterference of the electric signals with use of a shield conductor.

FIGS. 14A, 14B, and 14C illustrate a configuration example of thewireless communication system 100 for preventing or reducing theinterference of the electric signals with use of a shield conductorhaving a slit.

FIGS. 15A and 15B illustrate another configuration example of thewireless communication system 100 including the parallelly movablecouplers.

FIGS. 16A, 16B, and 16C illustrate another configuration example of thewireless communication system 100 including the rotatably movablecouplers.

FIGS. 17A and 17B illustrate another configuration example of thewireless communication system 100 including the rotatably movablecouplers.

FIGS. 18A and 18B illustrate another configuration example of thewireless communication system 100 including the rotatably movablecouplers.

FIGS. 19A, 19B, and 19C illustrate a simulation result regarding theinterference of the electric signals in the wireless communicationsystem 100 including the rotationally movable couplers.

FIGS. 20A, 20B, and 20C illustrate a simulation result regarding theinterference of the electric signals in the wireless communicationsystem 100 including the rotationally movable couplers in a case wherethe shield conductor is used.

FIGS. 21A, 21B, and 21C illustrate a simulation result regarding theinterference of the electric signals in the wireless communicationsystem 100 including the rotationally movable couplers in a case wherethe shield conductor having the slit is used.

DESCRIPTION OF THE EMBODIMENTS

<System Configuration>

In the following description, an exemplary embodiment will be describedwith reference to the drawings. FIG. 1 illustrates a systemconfiguration of a wireless communication system 100 (hereinafterreferred to as a system 100) according to the present exemplaryembodiment. The system 100 includes a communication apparatus 101, and acommunication apparatus 102 that carries out wireless communication withthe communication apparatus 101. The communication apparatus 101includes a transmission circuit 103, a transmission coupler 104, areception circuit 107, a reception coupler 108, and a control unit 111.Similarly, the communication apparatus 102 includes a reception circuit105, a reception coupler 106, a transmission circuit 109, a transmissioncoupler 110, and a control unit 112. The communication apparatus 101 andthe communication apparatus 102 can be a first portion and a secondportion of a single apparatus.

In the present exemplary embodiment, the system 100 includes a structurefor supporting the communication apparatus 101 and the communicationapparatus 102 to maintain a predetermined positional relationshiptherebetween (e.g., such a positional relationship that a distancebetween the couplers is kept substantially constant). More specifically,the communication apparatus 101 is a pan head portion of a networkcamera and the communication apparatus 102 is an imaging portion of thenetwork camera. In another example, the communication apparatus 101 is ahand portion of a robot arm and the communication apparatus 102 is anarm portion coupled with the hand portion. In yet another example, thecommunication apparatus 101 is a print head portion of a printer and thecommunication apparatus 102 is a main body portion of the printer. Howthe system 100 is applied is not limited to these examples.

The transmission coupler 104, the transmission coupler 110, thereception coupler 106, and the reception coupler 108 are each aplate-like conductor functioning as an antenna. However, the shapes ofthe couplers are not limited thereto. The transmission coupler 104functions as an antenna for carrying out wireless communication based onelectromagnetic field coupling with the reception coupler 106, and thetransmission coupler 110 functions as an antenna for carrying outwireless communication based on electromagnetic field coupling with thereception coupler 108.

The electromagnetic field coupling according to the present exemplaryembodiment includes both electric field coupling and magnetic fieldcoupling. In other words, the wireless communication between thecouplers can be carried out based on the electric field coupling, can becarried out based on the magnetic field coupling, or can be carried outbased on both the electric field coupling and the magnetic fieldcoupling. In FIG. 1, the communication apparatus 101 and thecommunication apparatus 102 each include the two couplers fortransmission and reception, but at least one or more of thecommunication apparatus 101 and the communication apparatus 102 caninclude three or more couplers.

The control unit 111 of the communication apparatus 101 controls thetransmission circuit 103 to perform processing for transmitting data tothe communication apparatus 102, and controls the reception circuit 107to perform processing for receiving data from the communicationapparatus 102. Similarly, the control unit 112 of the communicationapparatus 102 controls the transmission circuit 109 to performprocessing for transmitting the data to the communication apparatus 101,and controls the reception circuit 105 to perform processing forreceiving the data from the communication apparatus 101. The controlunit 111 can control a functional unit (not illustrated) included in thecommunication apparatus 101 based on the data that the communicationapparatus 101 receives by controlling the reception circuit 107.Similarly, the control unit 112 can control a functional unit (notillustrated) included in the communication apparatus 102 based on thedata that the communication apparatus 102 receives by controlling thereception circuit 105. Here, examples of the functional unit include adisplay control unit that causes an image based on the received data tobe displayed on a display unit, and a transfer unit that transfers thereceived data to an external apparatus.

The transmission circuit 103 generates an electric signal based on thecontrol by the control unit 111, and transmits the electric signal basedon the baseband method, which transmits the electric signal withoutmodulating it, from the transmission coupler 104 to the receptioncoupler 106. Similarly, the transmission circuit 109 generates anelectric signal based on the control by the control unit 112, andtransmits the electric signal based on the baseband method from thetransmission coupler 110 to the reception coupler 108. The receptioncircuit 107 transmits the electric signal received by the receptioncoupler 108 to the control unit 111. Similarly, the reception circuit105 transmits the electric signal received by the reception coupler 106to the control unit 112.

FIGS. 2A and 2B illustrate a configuration example of the transmissionand reception couplers in the system 100. FIG. 2A is a perspective viewof a part of the system 100, and FIG. 2B illustrates the part of thesystem 100 as viewed from an X-axis positive direction of a coordinatesystem 200 defined by an X axis, a Y axis, and a Z axis orthogonal toone another. The transmission coupler 104 and the reception coupler 108are mounted on the same surface of a plate-like member included in thecommunication apparatus 101, and are positioned on substantially thesame plane. The transmission coupler 110 and the reception coupler 106are mounted on the same surface of a plate-like member included in thecommunication apparatus 102, and are positioned on substantially thesame plane.

The transmission coupler 104 and the reception coupler 106 are locatedin proximity to each other and positioned to face each other in anZ-axis direction. In other words, the transmission coupler 104 and thereception 106 at least partially overlap each other when being viewedfrom the Z-axis direction. Similarly, the transmission coupler 110 andthe reception coupler 108 are located in proximity to each other andpositioned to face each other in the Z-axis direction. In such aconfiguration, the data transmission from the communication apparatus101 to the communication apparatus 102 is realized by the transmissionof the electric signal from the transmission coupler 104 to thereception coupler 106 in a Z-axis positive direction. The datatransmission from the communication apparatus 102 to the communicationapparatus 101 is realized by the transmission of the electric signalfrom the transmission coupler 110 to the reception coupler 108 in aZ-axis negative direction.

In FIGS. 2A and 2B, each of the couplers is illustrated as including along side substantially in parallel with an X-axis direction, but theshape and the mounting direction of each of the couplers are not limitedthereto and can be a different shape and a different direction as longas the corresponding transmission coupler and reception coupler canestablish the electromagnetic field coupling therebetween. For example,the transmission coupler 110 and the reception coupler 108 can each havea long side substantially in parallel with a Y-axis direction, and thetransmission coupler 104 and the reception coupler 106 can each have thelong side substantially in parallel with the X-axis direction.Alternatively, the transmission coupler 110 and the reception coupler106 can be arranged linearly in the X-axis direction, and thetransmission coupler 104 and the reception coupler 108 can be arrangedlinearly in the X-axis direction. The shape of the coupler can be aU-shape, an L-shape, or other shapes.

FIGS. 3A to 3F illustrate examples of waveforms of the electric signalstransmitted and received when the communication apparatus 101 and thecommunication apparatus 102 carry out the communication based on theelectric field coupling. A horizontal axis in each of FIGS. 3A to 3Findicates time. First, a first transmission signal illustrated in FIG.3A that is generated by the transmission circuit 103 is input to thetransmission coupler 104. The reception coupler 106 is coupled with thetransmission coupler 104 by the electric field coupling, so that a firstreception signal illustrated in FIG. 3B is generated at the receptioncoupler 106 based on the input of the first transmission signal to thetransmission coupler 104. The reception circuit 105 performs conversionprocessing on this first reception signal to generate a firstconversion-completed signal illustrated in FIG. 3C, which has a similarwaveform to the first transmission signal. The conversion processing bythe reception circuit 105 includes, for example, processing forconverting a received analog signal into a digital signal by comparingthis analog signal with a threshold value with use of a comparator.Transmission of a first electric signal from the communication apparatus101 to the communication apparatus 102 is realized by theabove-described process.

Transmission of a second electric signal from the communicationapparatus 102 to the communication apparatus 101 is also realized by asimilar process. More specifically, a second reception signalillustrated in FIG. 3E is generated at the reception coupler 108 basedon an input of a second transmission signal illustrated in FIG. 3D,which is generated by the transmission circuit 109, to the transmissioncoupler 110. Then, the reception circuit 107 performs the conversionprocessing on this second reception signal to generate a secondconversion-completed signal illustrated in FIG. 3F, which has a similarwaveform to the second transmission signal.

In this manner, the provision of the transmission coupler and thereception coupler to each of the communication apparatus 101 and thecommunication apparatus 102 enables bidirectional communication to becarried out between the communication apparatus 101 and thecommunication apparatus 102. The communication apparatus 101 can carryout the data transmission and the data reception using the differentcouplers for each of them asynchronously, and therefore can realizehigh-speed communication compared to, for example, alternately carryingout the transmission and the reception with use of a single coupler in atime-sharing manner.

In the above description, the present exemplary embodiment has beendescribed referring to the system 100 in which the communicationapparatus 101 and the communication apparatus 102 carry out thebidirectional communication therebetween, but two or more pairs ofcouplers can be used for unidirectional communication. FIG. 4illustrates a system configuration of a wireless communication system400 (hereinafter referred to as a system 400) in which theunidirectional commutation is carried out between a communicationapparatus 401 and a communication apparatus 402. The communicationapparatus 401 includes the transmission circuit 103, the transmissioncoupler 104, the transmission circuit 109, the transmission coupler 110,and the control unit 111. The communication apparatus 402 includes thereception circuit 105, the reception coupler 106, the reception circuit107, the reception coupler 108, and the control unit 112. Details ofeach of the components of the communication apparatus 401 and thecommunication apparatus 402 are similar to each of the componentsidentified by the same reference numerals in FIG. 1. However, thecontrol unit 111 does not have to perform the data reception processing,and the control unit 112 does not have to perform the data transmissionprocessing.

In the system 400, an electric signal is transmitted from thetransmission coupler 104 of the communication apparatus 401 to thereception coupler 106 of the communication apparatus 402. An electricsignal is transmitted from the transmission coupler 110 of thecommunication apparatus 401 to the reception coupler 108 of thecommunication apparatus 402. If the communication apparatus 401transmits different electric signals from the transmission coupler 104and the transmission coupler 110 simultaneously, the system 400 enablesa larger data amount to be transmitted per unit time than transmittingthe electric signals from the single transmission coupler, therebysucceeding in realizing further high-speed communication.

If the communication apparatus 401 transmits the same electric signalsfrom the transmission coupler 104 and the transmission coupler 110, evenwhen the data transmission using one of the transmission couplers hasfailed due to an influence of noise or the like, the system 400 enablesthe data to be transmitted to the communication apparatus 402 using theother of the transmission couplers. By this effect, the system 400 canreduce processing for retransmitting the data, which would be performed,for example, according to the failure in the communication, therebyrealizing further high-speed communication, compared to transmitting theelectric signal from the single transmission coupler.

In FIG. 4, the communication apparatus 401 includes the two couplers forthe transmission and the communication apparatus 402 includes the twocouplers for the reception, but the communication apparatus 401 caninclude three or more couplers for the transmission and thecommunication apparatus 402 can include three or more couplers for thereception. Alternatively, the communication apparatus 401 can includetwo or more couplers for the transmission and one or more couplers forthe reception, and the communication apparatus 402 can include one ormore couplers for the transmission and two or more couplers for thereception.

In FIGS. 1 and 4, the present exemplary embodiment has been describedreferring to the system 100 and the system 400 in which thecommunication is carried out between the two communication apparatuses,but the communication can be carried out among three or morecommunication apparatuses. FIG. 5 illustrates a system configuration ofa wireless communication system 500 (herein after referred to as asystem 500), in which the communication is carried out among threecommunication apparatuses, i.e., a communication apparatus 501, acommunication apparatus 502, and a communication apparatus 503. Thecommunication apparatus 501 includes the transmission circuit 103, thetransmission coupler 104, and the control unit 111. The communicationapparatus 502 includes the reception circuit 105, the reception coupler106, the transmission circuit 109, the transmission coupler 110, and thecontrol unit 112. The communication apparatus 503 includes the receptioncircuit 107, the reception coupler 108, and a control unit 113.

Details of each of the components of the communication apparatus 501,the communication apparatus 502, and the communication apparatus 503 aresimilar to each of the components identified by the same referencenumerals in FIG. 1. The control unit 113 performs similar communicationprocessing to the control unit 111 and the control unit 112. However,the control unit 111 does not have to perform the data receptionprocessing, and the control unit 113 does not have to perform the datatransmission processing. In the system 500, an electric signal istransmitted from the transmission coupler 104 of the communicationapparatus 501 to the reception coupler 106 of the communicationapparatus 502, and an electric signal is transmitted from thetransmission coupler 110 of communication apparatus 502 to the receptioncoupler 108 of the communication apparatus 503.

In FIGS. 1, 4, and 5, the present exemplary embodiment has beendescribed referring to the example in which the coupler for thetransmission and the coupler for the reception are used while beingdistinguished from each other, but one coupler can be used for both thetransmission and the reception. For example, the system 100 illustratedin FIG. 1 can be configured such that the reception circuit 107 includesboth the function as the circuit for the reception and the function asthe circuit for the transmission, and the control unit 111 switcheswhether to cause the reception circuit 107 to function as the circuitfor the transmission or function as the circuit for the reception. Whenthe reception circuit 107 functions as the circuit for the transmission,an electric signal is transmitted from the reception coupler 108 to thetransmission coupler 110.

In the case where such processing for switching the transmission and thereception is performed in the communication apparatus 101, in thecommunication apparatus 102, the transmission circuit 109 also includesboth the function as the circuit for the transmission and the functionas the circuit for the reception, and the processing for switching thetransmission and the reception is also performed by the control unit112. In other words, whether to transmit the electric signal from thetransmission coupler 110 to the reception coupler 108 or transmit theelectric signal from the reception coupler 108 to the transmissioncoupler 110 is controlled by the control unit 111 and the control unit112.

With such a configuration, the system 100 can control whether to carryout the bidirectional communication or carry out the unidirectionalcommunication between the communication apparatus 101 and thecommunication apparatus 102. For example, one conceivable situation isthat the data that should be transmitted from the communicationapparatus 102 to the communication apparatus 101 occurs less frequentlythan the data that should be transmitted from the communicationapparatus 101 to the communication apparatus 102 occurs. Under such asituation, the system 100 can carry out the bidirectional communicationby transmitting the data from the transmission coupler 104 to thereception coupler 106 and also transmitting the data from thetransmission coupler 110 to the reception coupler 108 during a timeperiod when there is the data that should be transmitted from thecommunication apparatus 102. The system 100 can carry out theunidirectional communication by transmitting the data from thetransmission coupler 104 to the reception coupler 106 and alsotransmitting the data from the reception coupler 108 to the transmissioncoupler 110 during a time period when there is not the data that shouldbe transmitted from the communication apparatus 102. By operating inthis manner, the system 100 can efficiently use the coupler according tothe data that should be communicated, thereby realizing the high-speedcommunication.

The present exemplary embodiment is being described focusing on theexample in which the wireless communication is carried out bysingle-ended transmission, but is not limited thereto. The wirelesscommunication can be carried out by differential transmission. Forexample, in a case where the differential transmission is applied to thesystem 100 illustrated in FIG. 1, the system 100 is modified asindicated by a system 600 illustrated in FIG. 6, with each of thetransmission coupler 104, the reception coupler 106, the receptioncoupler 108, and the transmission coupler 110 being replaced with twocouplers for transmitting signals opposite in phase from each other. InFIG. 6, similar components to the system 100 illustrated in FIG. 1 areidentified by the same reference numerals.

In the system 600, the communication apparatus 101 includes atransmission coupler 114 and a reception coupler 118, and thecommunication apparatus 102 includes a reception coupler 116 and atransmission coupler 120, in addition to the configuration of the system100. The transmission coupler 114 functions as an antenna for carryingout wireless communication based on electromagnetic field coupling withthe reception coupler 116, and the transmission coupler 120 functions asan antenna for carrying out wireless communication based onelectromagnetic field coupling with the reception coupler 118.

The transmission circuit 103 transmits a signal opposite in phase fromthe electric signal transmitted from the transmission coupler 104 to thereception coupler 106, from the transmission coupler 114 to thereception coupler 116. The transmission circuit 109 transmits a signalopposite in phase from the electric signal transmitted from thetransmission coupler 110 to the reception coupler 108, from thetransmission coupler 120 to the reception coupler 118. Then, thereception circuit 105 transfers a potential difference between theelectric signal received by the reception coupler 106 and the electricsignal received by the reception coupler 116 to the control unit 112.Similarly, the reception circuit 107 transfers a potential differencebetween the electric signal received by the reception coupler 108 andthe electric signal received by the reception coupler 118 to the controlunit 111.

The configuration like the system 600 enables the communicationapparatus 101 and the communication apparatus 102 to carry out thewireless communication by the differential transmission therebetween.Using the differential transmission achieves a lower influence ofexternal noise in the wireless communication than using the single-endedtransmission. In FIG. 6, the system 600 has been described referring tothe example in which the differential transmission is applied to thesystem 100 illustrated in FIG. 1. The differential transmission,however, can similarly be applied to the system 400 illustrated in FIG.4 and the system 500 illustrated in FIG. 5. The differentialtransmission can be applied to the system including the above-describedcouplers that switch the transmission and the reception.

<Prevention or Reduction of Interference>

In the descriptions of the above-described drawings, FIGS. 3A to 3F, thewaveforms have been described referring to the examples of the waveformsin the case where no interference occurs in the electric signalstransmitted and received between the two pairs of couplers. Interferencecan occur in the transmitted and received electric signals depending on,for example, the positional relationship among the individual couplers.For example, suppose that, in FIG. 2, the transmission coupler 104 andthe reception coupler 108 are located just a short distance away fromeach other in the Y-axis direction, and the reception coupler 106 andthe transmission coupler 110 are located just a short distance away fromeach other in the Y-axis direction. In such a case, the electric signaltransmitted from the transmission coupler 104 can accidentally bereceived by the reception coupler 108, and the electric signaltransmitted from the transmission coupler 110 can accidentally bereceived by the reception coupler 106.

FIGS. 7A to 7F illustrate examples of waveforms of the electric signalstransmitted and received between the communication apparatus 101 and thecommunication apparatus 102 of the system 100 in the case where theinterference has occurred. A horizontal axis in each of FIGS. 7A to 7Findicates time. First, a first transmission signal illustrated in FIG.7A that is generated by the transmission circuit 103 is input to thetransmission coupler 104, and a second transmission signal illustratedin FIG. 7D that is generated by the transmission circuit 109 is input tothe transmission coupler 110. At this time, the reception coupler 106also receives the signal transmitted from the transmission coupler 110accidentally in addition to the signal transmitted from the transmissioncoupler 104, and noise 701 is contained in the first reception signalgenerated at the reception coupler 106 as illustrated in FIG. 7B. Whenthe conversion processing by the reception circuit 105 is performed onthis first reception signal, a first conversion-completed signalcontaining noise 702 therein is generated as illustrated in FIG. 7C.Similarly, noise 703 is contained in the second reception signalgenerated at the reception coupler 108 due to an influence of the signaltransmitted from the transmission coupler 104, as illustrated in FIG.7E. Then, when the conversion processing by the reception circuit 107 isperformed on the second reception signal, a second conversion-completedsignal containing noise 704 therein is generated as illustrated in FIG.7F.

In the following description, a configuration of the system 100 forpreventing or reducing the occurrence of the noise due to theinterference of the electric signals like the examples illustrated inFIGS. 7A to 7F will be described. The configuration that will bedescribed below can be applied to the system 100 illustrated in FIG. 1as well as to the above-described configurations such as the system 400illustrated in FIG. 4 and the system 600 illustrated in FIG. 6 in asimilar manner.

A configuration example of the system 100 for preventing or reducing theinterference of the electric signals will be described with reference toFIGS. 8A and 8B. FIG. 8A is a perspective view of a part of the system100, and FIG. 8B illustrates the part of the system 100 as viewed fromthe X-axis positive direction of the coordinate system 200. In FIGS. 8Aand 8B, similar components to FIGS. 2A and 2B are identified by the samereference numerals.

In FIGS. 8A and 8B, the communication apparatus 101 includes a ground801 positioned between the transmission coupler 104 and the receptioncoupler 108, and the communication apparatus 102 includes a ground 802positioned between the reception coupler 106 and the transmissioncoupler 110, to prevent or reduce the above-described interference. Eachof the ground 801 and the ground 802 is, for example, a conductorconnected to a reference potential point. In FIGS. 8A and 8B, the ground801 and the ground 802 have shapes longer in length in the X-axisdirection than the couplers, but the shapes of the ground 801 and theground 802 are not limited thereto.

The provision of the ground 801 to the communication apparatus 101weakens the electromagnetic field coupling between the transmissioncoupler 104 and the reception coupler 108, thereby contributing topreventing or reducing the occurrence of the noise in the electricsignal received by the reception coupler 108. Similarly, the provisionof the ground 802 to the communication apparatus 102 weakens theelectromagnetic field coupling between the transmission coupler 110 andthe reception coupler 106, thereby contributing to preventing orreducing the occurrence of the noise in the electric signal received bythe reception coupler 106. The system 100 can include only one or moreof the ground 801 and the ground 802.

Alternatively, as another configuration example for preventing orreducing the interference, the couplers can be disposed such that thedistance between the transmission coupler 104 and the reception coupler108 in the Y-axis direction, and the distance between the receptioncoupler 106 and the transmission coupler 110 in the Y-axis directionmatch or exceed a predetermined distance. The above-describedpredetermined distance is set according to, for example, strength of thetransmitted signal and/or allowable strength of noise.

Alternatively, as another configuration example for preventing orreducing the interference, the transmission and the reception can becarried out in a time-sharing manner in the communication between thecommunication apparatus 101 and the communication apparatus 102. Morespecifically, the control unit 111 and the control unit 112 can controlthe transmission circuit 103 and the transmission circuit 109,respectively, to prevent the electric signals from being simultaneouslytransmitted from the transmission coupler 104 to the reception coupler106 and from the transmission coupler 110 to the reception coupler 108.

In the above description with reference to FIGS. 8A and 8B, the ground801 and the ground 802 each connected to the reference potential pointare assumed to be used as the conductor disposed between thetransmission coupler and the reception coupler. However, the conductordisposed between the transmission coupler and the reception coupler isnot limited thereto, and a conductor isolated from a so-called electricground of the transmission circuit or the reception circuit in terms ofa direct current or an alternating current can be disposed on at leastone of a position between the transmission coupler 104 and the receptioncoupler 108 and a position between the transmission coupler 110 and thereception coupler 106.

Next, as another configuration example for preventing or reducing theinterference, the system 100 including couplers with different lengthsfrom FIGS. 2A and 2B will be described with reference to FIGS. 9A to 9D.FIG. 9A is a perspective view of a part of the system 100, and FIG. 9Billustrates the part of the system 100 as viewed from the X-axispositive direction of the coordinate system 200. FIG. 9C illustrates thepart of the system 100 as viewed from the Z-axis positive direction, andFIG. 9D illustrates the part of the system 100 as viewed from the Z-axisnegative direction. In FIGS. 9A to 9D, similar components to FIGS. 2Aand 2B are identified by the same reference numerals. In FIGS. 9B to 9D,a reception coupler 906 and the transmission coupler 110 of thecommunication apparatus 102 are illustrated in white for illustrativepurposes.

In the configuration illustrated in FIGS. 9A to 9D, the receptioncoupler 106 and the reception coupler 108 illustrated in FIGS. 2A and 2Bare replaced with the reception coupler 906 and a reception coupler 908with shorter lengths in the X-axis direction. Here, each of the couplershas a flat shape as illustrated in FIG. 9B, and therefore an area of aportion of the transmission coupler 110 that faces the reception coupler908 is larger than an area of a portion of the transmission coupler 110that faces the reception coupler 906. With such a configuration, weakerelectromagnetic field coupling is established between the transmissioncoupler 110 and the reception coupler 906 than the electromagnetic fieldcoupling between the transmission coupler 110 and the reception coupler106 illustrated in FIGS. 2A and 2B. Similarly, weaker electromagneticfield coupling is established between the transmission coupler 104 andthe reception coupler 908 than the electromagnetic field couplingbetween the transmission coupler 104 and the reception coupler 108illustrated in FIGS. 2A and 2B. As a result, the system 100 can preventor reduce the occurrence of the noise due to the interference of theelectric signals transmitted and received between the communicationapparatus 101 and the communication apparatus 102.

<Movement of Coupler Position>

In the above description, the present exemplary embodiment has beendescribed referring to the example in which a positional relationshipbetween the couplers is fixed, but relative positions of the couplerscan be variable. In the following description, a configuration of thesystem 100 that can move the relative positions of the couplers whilemaintaining the state of carrying out the wireless communication will bedescribed. The configuration that will be described below can also beapplied to the above-described configurations, such as the system 400illustrated in FIG. 4 and the system 600 illustrated in FIG. 6 in asimilar manner.

A configuration example of the system 100 including parallelly movablecouplers will be described with reference to FIGS. 10A and 10B. In FIGS.10A and 10B, similar components to FIGS. 2A and 2B are identified by thesame reference numerals. Unlike the configuration in the case of FIGS.2A and 2B, the transmission coupler 104 and the reception coupler 108are mounted on opposite sides of the surface of the plate-like memberincluded in the communication apparatus 101 from each other. Thecommunication apparatus 102 includes two plate-like members tovertically surround the plate-like member included in the communicationapparatus 101, with a transmission coupler 1010 mounted on one of thesetwo plate-like members and a reception coupler 1006 mounted on the otherof these two plate-like members. In other words, the transmissioncoupler 1010 and the reception coupler 1006 are positioned on oppositesides of the surface of the plate-like member included in thecommunication apparatus 101 from each other.

With such a configuration, weaker electromagnetic field coupling isestablished between the transmission coupler 1010 and the receptioncoupler 1006 than the electromagnetic field coupling between thetransmission coupler 110 and the reception coupler 106 illustrated inFIGS. 2A and 2B. Weaker electromagnetic field coupling is establishedbetween the transmission coupler 104 and the reception coupler 108 thanthe electromagnetic field coupling in the case of FIGS. 2A and 2B. As aresult, the system 100 prevents or reduces interference between anelectric signal transmitted from the transmission coupler 1010 to thereception coupler 108 and an electric signal transmitted from thetransmission coupler 104 to the reception coupler 1006.

The interference of the electric signals can also be prevented orreduced by setting up a ground at a position between the transmissioncoupler 104 and the reception coupler 108, such as an inner layer of theplate-like member included in the communication apparatus 101. In thecase where the interference can be prevented or reduced in this manner,the distance between the transmission coupler 104 and the receptioncoupler 108 in the Y-axis direction can be shortened by, for example,mounting the transmission coupler 104 and the reception coupler 108 atcorresponding positions on a back surface and a front surface of theplate-like member, respectively. As a result, this configuration alsoenables the communication apparatus 101 and the communication apparatus102 to be reduced in size in the Y-axis direction.

The transmission coupler 1010 and the reception coupler 1006 illustratedin FIGS. 10A and 10B are shorter in length in the X-axis direction thanthe transmission coupler 110 and the reception coupler 106 illustratedin FIGS. 2A and 2B. Therefore, the transmission coupler 1010 is shorterin length in the X-axis direction than the reception coupler 108, andthe reception coupler 1006 is shorter in length in the X-axis directionthan the transmission coupler 104. This enables the communicationapparatus 102 to be reduced in size in the X-axis direction.

The communication apparatus 102 is movable in the X-axis direction ofthe coordinate system 200 while keeping the transmission coupler 1010and the reception coupler 108 facing each other and the transmissioncoupler 104 and the reception coupler 1006 facing each other. Control ofthe movement of the communication apparatus 102 can be realized by, forexample, controlling a driving unit (not illustrated) included in thecommunication apparatus 102 by the control unit 112. This control of themovement enables a position of the transmission coupler 1010 relative tothe reception coupler 108, and a position of the transmission coupler104 relative to the reception coupler 1006 to be moved in the X-axisdirection.

The communication apparatus 101 can be moved in the X-axis directioninstead of the communication apparatus 102, or both the communicationapparatus 101 and the communication apparatus 102 cam be moved. Thedirection in which the couplers are moved is not limited to the X-axisdirection and can be another direction. Without being limited to therange that keeps the transmission coupler and the reception couplerfacing each other, the couplers can be moved in a range that enables thecommunication based on the electromagnetic field coupling to be carriedout between the transmission coupler and the reception coupler. In thesystem 100 described with reference to FIGS. 2A and 2B, 8A and 8B, and9A, 9B, 9C, and 9D, at least one or more of the communication apparatus101 and the communication apparatus 102 can be moved in the X-axisdirection.

Next, a configuration example of the system 100 including rotationallymovable couplers will be described with reference to FIGS. 11A, 11B, and11C. FIG. 11A is a perspective view of a part of the system 100. FIG.11B illustrates the part of the system 100 as viewed from the Z-axispositive direction of the coordinate system 200. FIG. 11C illustratesthe part of the system 100 as viewed from the Z-axis negative direction.In FIGS. 11A, 11B, and 11C, components similar to those in FIGS. 2A and2B are identified by the same reference numerals.

A transmission coupler 1104 and a reception coupler 1108 are mounted ona cylindrical member included in the communication apparatus 101, and atransmission coupler 1110 and a reception coupler 1106 are mounted on acylindrical member included in the communication apparatus 102. Thecylindrical member included in the communication apparatus 101 and thecylindrical member included in the communication apparatus 102 includecentral axes substantially coinciding with each other and differentdiameters from each other. The transmission coupler 1104 faces thereception coupler 1106 and the transmission coupler 1110 faces thereception coupler 1108. In other words, the reception coupler 1108 andthe transmission coupler 1110 are positioned substantially oncircumferences of circles centered at the same point as each other andhaving different diameters from each other, respectively. Thetransmission coupler 1104 and the reception coupler 1106 are positionedsubstantially on circumferences of circles centered at the same point aseach other and having different diameters from each other, respectively.

In such a configuration, an electric signal is transmitted from thetransmission coupler 1104 to the reception coupler 1106 based onelectromagnetic field coupling, and an electric signal is transmittedfrom the transmission coupler 1110 to the reception coupler 1108 basedon electromagnetic field coupling. A diameter of a cylinder along aportion of which the transmission coupler 1104 is mounted and a diameterof a cylinder along a portion of which the reception coupler 1108 ismounted can be different from each other. Similarly, a diameter of acylinder along a portion of which the transmission coupler 1110 ismounted and a diameter of a cylinder along a portion of which thereception coupler 1106 is mounted can be different from each other.

The communication apparatus 102 is rotationally movable around thecentral axis of the cylindrical member (axis in the Z-axis direction)while keeping the transmission coupler 1104 and the reception coupler1106 to face each other and the transmission coupler 1110 and thereception coupler 1108 to face each other. Control of the movement ofthe communication apparatus 102 can be realized by, for example,controlling a driving unit (not illustrated) included in thecommunication apparatus 102 by the control unit 112. This control of themovement enables the transmission coupler 1110 and the reception coupler1106 to be rotationally moved. The communication apparatus 101 can berotationally moved around the central axis of the cylindrical memberinstead of the communication apparatus 102, thereby causing thetransmission coupler 1104 and the reception coupler 1108 to berotationally moved. Alternatively, both the communication apparatus 101and the communication apparatus 102 can be rotationally moved.

As illustrated in FIGS. 11B and 11C, the reception coupler 1106 and thereception coupler 1108 each have an arc shape from a viewpoint of areference direction (Z-axis direction) substantially in parallel withthe central axis of the cylindrical member. The transmission coupler1104 and the transmission coupler 1110 each have a substantiallycircular shape from the viewpoint of this reference direction. Thetransmission coupler 1104 with the substantially circular shape enablesthe transmission coupler 1104 and the reception coupler 1106 to faceeach other regardless of how large the rotational angle is with respectto the rotational movement of the reception coupler 1106. The receptioncoupler 1106 with the arc shape can weaken the electromagnetic fieldcoupling between the transmission coupler 1110 and the reception coupler1106 compared to the reception coupler 1106 with a substantiallycircular shape. The same applies to the shapes of the transmissioncoupler 1110 and the reception coupler 1108. As a result, the system 100prevents or reduces the interference between the electric signaltransmitted from the transmission coupler 1104 to the reception coupler1106, and the electric signal transmitted from the transmission coupler1110 to the reception coupler 1108.

The interference can also be prevented or reduced by disposing a groundon one or more of a position between the transmission coupler 1104 andthe reception coupler 1108 of the communication apparatus 101 and aposition between the reception coupler 1106 and the transmission coupler1110 of the communication apparatus 102.

The shape of each of the couplers is not limited to the exampleillustrated in FIGS. 11A, 11B, and 11C. For example, one or more of thetransmission coupler 1104 and the transmission coupler 1110 can have anarc shape, and at least any one of the reception coupler 1106 and thereception coupler 1108 can have a substantially circular shape.Alternatively, both the transmission coupler 1104 and the receptioncoupler 1106 can each have an arc shape. In this case, the couplers canbe rotationally moved only in a range enabling the transmission coupler1104 and the reception coupler 1106 to face each other or a rangeenabling the communication based on the electromagnetic field couplingto be carried out between the transmission coupler 1104 and thereception coupler 1106. The same applies in a case where both thetransmission coupler 1110 and the reception coupler 1108 each have anarc shape.

As an exemplary modification of the configuration illustrated in FIGS.11A, 11B, and 11C, the system 100 can be configured as if theconfiguration illustrated in FIGS. 10A and 10B is rounded around theY-axis direction. More specifically, the configuration illustrated inFIGS. 11A, 11B, and 11C can be configured in the following manner. Thereception coupler 108 and the transmission coupler 104 are mounted on aninner surface and an outer surface of a cylindrical member included inthe communication apparatus 101, respectively. The communicationapparatus 102 sandwiches this cylindrical member in such a manner thatthe transmission coupler 1010 mounted on the communication apparatus 102is positioned inside this cylindrical member and the reception coupler1006 mounted on the communication apparatus 102 is positioned outsidethis cylindrical member. Similarly, the transmission coupler 104 and thereception coupler 108 can be mounted on the inner surface and the outersurface of the cylindrical member included in the communicationapparatus 101, respectively. In such a configuration, one or more of thecommunication apparatus 101 and the communication apparatus 102 can berotationally moved around the Y-axis direction.

In this exemplary modification, the interference of the electric signalscan be prevented or reduced by disposing a ground between thetransmission coupler 104 and the reception coupler 108, such as theinner layer of the cylindrical member included in the communicationapparatus 101. In the case where the interference can be prevented orreduced in this manner, the distance between the transmission coupler104 and the reception coupler 108 in the Y-axis direction can beshortened by, for example, mounting the transmission coupler 104 and thereception coupler 108 at corresponding positions on the inner surfaceand the outer surface of the cylindrical member, respectively. As aresult, this configuration enables the communication apparatus 101 andthe communication apparatus 102 to be reduced in size in the Y-axisdirection.

<Specific Configuration Example of Coupler>

FIGS. 12A, 12B, and 12C illustrate specific configuration examples ofthe couplers in the wireless communication system 600 to which thedifferential transmission is applied, which has been described abovewith reference to FIG. 6. FIGS. 12A, 12B, and 12C illustrate specificconfiguration examples of the couplers in cases where the wirelesscommunication is realized by the electric field coupling, the magneticfield coupling, and the electric field and magnetic field coupling,respectively. Hereinafter, the couplers illustrated in FIGS. 12A, 12B,and 12C will be referred to as a coupler for electric field coupling, acoupler for magnetic field coupling, and a coupler for electromagneticfield coupling, respectively.

In the coupler for electric field coupling illustrated in FIG. 12A, thetransmission coupler formed by the two conductors (transmission coupler104 and transmission coupler 114) is electrically opened at an oppositeend from a power supply point (P1) connected to the transmission circuit103. Similarly, the reception coupler formed by the two conductors(reception coupler 106 and reception coupler 116) is electrically openedat an opposite end from a power supply point (P2) connected to thereception circuit 105. In the coupler for magnetic field couplingillustrated in FIG. 12B, the opposite ends of the transmission couplerand the reception coupler from the power supply points (P1 and P2) areelectrically short-circuited by a conductor 1200 and a conductor 1201,respectively. In the coupler for electromagnetic field couplingillustrated in FIG. 12C, a resistor 1202 substantially matching acharacteristic impedance of a transmission line connecting thetransmission circuit 103 and the transmission coupler therebetween isinserted at the opposite end of the transmission coupler from the powersupply point (P1). Similarly, a resistor 1203 substantially matching acharacteristic impedance of a transmission line connecting the receptioncircuit 105 and the reception coupler therebetween is inserted at theopposite end of the reception coupler from the power supply point (P2).

The shapes of the couplers based on each of the methods illustrated inFIGS. 12A to 12C are just one example, and are not limited thereto aslong as the couplers have the above-described characteristics. Thewireless communication using the couplers configured as illustrated inFIGS. 12A, 12B, and 12C is not limited to the differential transmission,and the wireless communication by the single-ended transmission can becarried out using the couplers configured as illustrated in FIGS. 12A,12B, and 12C.

<Prevention or Reduction of Interference by Shield Insertion>

The configuration of the system 100 for preventing or reducing theinterference of the electric signals has been described above withreference to FIGS. 8A and 8B, and 9A, 9B, 9C, and 9D, and, in thefollowing description, another configuration example of the system 100for preventing or reducing the interference will be described withreference to FIGS. 13A, 13B, and 13C. FIG. 13A is a perspective view ofa part of the system 100, and FIG. 13B illustrates the part of thesystem 100 as viewed from the X-axis positive direction of thecoordinate system 200. FIG. 13C illustrates the part of the system 100as viewed from the Z-axis positive direction of the coordinate system200. In FIG. 13C, the configuration of the communication apparatus 101side is omitted and only the configuration of the communicationapparatus 102 side is illustrated.

In the configuration illustrated in FIGS. 13A, 13B, and 13C, thecommunication apparatus 101 includes a plate-like shield conductor 1300.The shield conductor 1300 is disposed to overlap the transmissioncoupler 104 and the reception coupler 108 when being viewed from theZ-axis positive direction, and is also disposed on an opposite side ofthe transmission coupler 104 and the reception coupler 108 from thetransmission coupler 110 and the reception coupler 106. In other words,the shield conductor 1300 is disposed to cover the transmission coupler104 and the reception coupler 108 when being viewed from the Z-axisnegative direction. Similarly, the communication apparatus 102 includesa shield conductor 1301, and the shield conductor 1301 is disposed tocover the transmission coupler 110 and the reception coupler 106 whenbeing viewed from the Z-axis positive direction.

The interference of the electric signals that is generated between thetransmission coupler 104 and the reception coupler 108 like the exampledescribed with reference to FIGS. 7A to 7F can be prevented or reducedby disposing the shield conductor close to the couplers in theabove-described manner. The shield conductors 1300 and 1301 can be anymembers as long as they are conductors, and, for example, are made usingaluminum, copper, or the like. In a case where a substrate pattern suchas Flame Retardant Type 4 (FR4) is used, the shield conductors 1300 and1301 can be each formed using a conductor layer that is a surface layerdifferent from the layer on which the couplers are formed or an innerlayer. The shield conductors 1300 and 1301 can be connected in terms ofa direct current to or isolated in terms of a direct current/alternatingcurrent from the electric ground of the transmission circuit or thereception circuit. The shield conductor can be provided to only any oneof the communication apparatus 101 and the communication apparatus 102.The shield conductors 1300 and 1301 do not have to entirely cover thetransmission coupler and the reception coupler when being viewed fromthe Z-axis direction, and can be configured in a different manner aslong as at least a part of the transmission coupler or the receptioncoupler and the shield conductor overlap each other.

The interference of the electric signals between the couplers can beprevented or reduced by using a shield conductor including a slit. Thisconfiguration will be described with reference to FIGS. 14A, 14B, and14C. FIG. 14A is a perspective view of a part of the system 100, andFIG. 14B illustrates the part of the system 100 as viewed from theX-axis positive direction of the coordinate system 200. FIG. 14Cillustrates the part of the system 100 as viewed from the Z-axispositive direction of the coordinate system 200. In FIG. 14C, theconfiguration of the communication apparatus 101 side is omitted andonly the configuration of the communication apparatus 102 side isillustrated.

In the configuration illustrated in FIGS. 14A, 14B, and 14C, thecommunication apparatus 101 and the communication apparatus 102 includea shield conductor 1400 and a shield conductor 1401 with slits insertedtherein, respectively. The slit included in the shield conductor 1400 ispositioned between the transmission coupler 104 and the receptioncoupler 108 when being viewed from the Z-axis direction. Similarly, theslit included in the shield conductor 1401 is positioned between thetransmission coupler 110 and the reception coupler 106 when being viewedfrom the Z-axis direction.

The interference of the electric signals due to the coupling between thetransmission coupler 104 and the reception coupler 108 via the shieldconductor 1400 can be prevented or reduced by disposing the shieldconductor 1400 including the slit close to the couplers in theabove-described manner. The methods for preventing or reducing theinterference of the electric signals between the couplers that have beendescribed with reference to FIGS. 13A, 13B, and 13C, and 14A, 14B, and14C are especially effective in the case where the coupler for electricfield coupling is used.

<Sliding Movement of Coupler>

The configuration example of the system 100 including the parallellymovable couplers has been described above with reference to FIGS. 10Aand 10B, and an example in a case where couplers configured in adifferent manner from FIGS. 10A and 10B are applied to the parallellymovable system 100 will be described with reference to FIGS. 15A and15B. FIG. 15A is a perspective view of a part of the system 100, andFIG. 15B illustrates the part of the system 100 as viewed from theX-axis positive direction of the coordinate system 200.

In the configuration illustrated in FIGS. 15A and 15B, the transmissioncoupler 104 and the reception coupler 108 included in the communicationapparatus 101 are substantially equal in length, and are arranged sideby side in the Y-axis direction. The transmission coupler 104 and thereception coupler 108 are shorter in length in the X-axis directioncompared to a transmission coupler 1510 and a reception coupler 1506included in the communication apparatus 102. The communication apparatus101 is movable in the X-axis direction in a range where the transmissioncoupler 104 and the reception coupler 1506 overlap each other and thetransmission coupler 1510 and the reception coupler 108 overlap eachother when being viewed from the Z-axis positive direction, i.e., arange where the communication apparatus 101 and the communicationapparatus 102 are efficiently communicable with each other. Thecommunication apparatus 102 can be moved in a similar range instead ofthe communication apparatus 101, or both the communication apparatus 101and the communication apparatus 102 can be moved.

In the configuration example illustrated in FIGS. 15A and 15B, a groundconductor can be disposed between the transmission coupler 104 and thereception coupler 108 and/or between the transmission coupler 1510 andthe reception coupler 1506 as described with reference to FIGS. 8A and8B for the purpose of preventing or reducing the interference of theelectric signal between the couplers. Alternatively, in theconfiguration example illustrated in FIGS. 15A and 15B, a shieldconductor can be provided as described with reference to FIGS. 13A, 13B,and 13C, and 14A, 14B, and 14C for the purpose of preventing or reducingthe interference of the electric signal between the couplers.

In the configuration examples illustrated in FIGS. 9A, 9B, 9C, and 9D,and 10A and 10B, the configuration for preventing or reducing theinterference such as the above-described ground and shield can beapplied for the purpose of preventing or reducing the interference ofthe electric signal between the couplers. The plurality ofabove-described methods for preventing or reducing the interference canbe used in combination in a single system.

<Rotationally Movable System (Three-Dimensional Type)>

In the above description made referring to FIGS. 11A, 11B, and 11C, theconfiguration enabling the couplers to be rotationally moved bydisposing them on the cylindrical members has been described focusing onthe example in which the transmission coupler and the reception couplerhave different lengths from each other, but is not limited thereto. Forexample, in a case where the transmission coupler and the receptioncoupler are disposed away from each other by a distance long enough toraise no problem regarding the interference of the electric signalsbetween the transmission coupler and reception coupler disposed on oneof the communication apparatuses 101 and 102, the transmission couplerand the reception coupler can have equal lengths to each other asillustrated in FIGS. 16A, 16B, and 16C. In the configuration illustratedin FIGS. 16A, 16B, and 16C, the communication apparatus 101 includes atransmission coupler 1604 and a reception coupler 1608, and thecommunication apparatus 102 includes a transmission coupler 1610 and areception coupler 1606. The transmission coupler 1604 carries outcommunication with the reception coupler 1606, and the transmissioncoupler 1610 carries out communication with the reception coupler 1608.Such a configuration also enables the communication to be carried outwhile at least one of the communication apparatus 101 and thecommunication apparatus 102 is rotationally moved around the Z axissimilarly to the configuration described above with reference to FIGS.11A, 11B, and 11C.

In the configuration example illustrated in FIGS. 16A, 16B, and 16C, aground conductor can be disposed between the transmission coupler 1604and the reception coupler 1608 and/or the reception coupler 1606 and thetransmission coupler 1610 as described with reference to FIGS. 8A and 8Bfor the purpose of preventing or reducing the interference of theelectric signal between the couplers. Alternatively, in theconfiguration example illustrated in FIGS. 16A, 16B, and 16C, a shieldconductor can be provided as described with reference to FIGS. 13A, 13B,and 13C, and 14A, 14B, and 14C for the purpose of preventing or reducingthe interference of the electric signal between the couplers.

In the configuration illustrated in FIGS. 16A, 16B, and 16C, thetransmission coupler and the reception coupler are assumed to bedisposed on the same surface of the cylindrical member in each of thecommunication apparatus 101 and the communication apparatus 102.However, the positions of the transmission coupler and the receptioncoupler are not limited thereto, and the transmission coupler and thereception coupler can be disposed on different surfaces of thecylindrical member as illustrated in FIGS. 17A and 17B for the purposeof preventing or reducing the interference of the electric signalbetween the couplers. In the configuration illustrated in FIGS. 17A and17B, the communication apparatus 101 includes a cylindrical member A anda cylindrical member B, and the communication apparatus 102 includes acylindrical member C. The cylindrical member C is disposed inside thecylindrical member A, and the cylindrical member B is disposed furtherinside the cylindrical member C. A transmission coupler 1704 included inthe communication apparatus 101 is disposed on an inner surface of thecylindrical member A, and carries out communication with a receptioncoupler 1706 included in the communication apparatus 102 that isdisposed on an outer surface of the cylindrical member C. A transmissioncoupler 1710 included in the communication apparatus 102 is disposed onan inner surface of the cylindrical member C, and carries outcommunication with a reception coupler 1708 included in thecommunication apparatus 101 that is disposed on an outer surface of thecylindrical member B.

Such a configuration also enables the communication to be carried outwhile at least one of the communication apparatus 101 and thecommunication apparatus 102 is rotationally moved around the Z axissimilarly to the configurations described with reference to FIGS. 11A,11B, and 11C, and 16A, 16B, and 16C. In this case, each of thecylindrical members is supported by a structure not obstructing therotational movement so that a positional relationship thereof is notlargely changed.

A cylindrical shield conductor can be provided inside the cylindricalmember C to be sandwiched between the reception coupler 1706 and thetransmission coupler 1710 for the purpose of preventing or reducing theinterference of the electric signals between the reception coupler 1706and the transmission coupler 1710 included in the communicationapparatus 102. This shield conductor can be connected in terms of adirect current to or can be configured to be isolated in terms of adirect current/alternating current from the electric ground of thetransmission circuit or the reception circuit. In the configurationexamples illustrated in FIGS. 11A, 11B, and 11C, 16A, 16B, and 16C, and17A and 17B, the plurality of configurations for preventing or reducingthe interference of the electric signal between the couplers can be usedin combination.

<Rotationally Movable System (Planar Type)>

Another configuration example in which the couplers are rotationallymovable will be described with reference to FIGS. 18A and 18B. FIG. 18Ais a perspective view of a part of the system 100, and FIG. 18Billustrates the part of the system 100 as viewed from the X-axispositive direction of the coordinate system 200. In the configurationexample illustrated in FIGS. 18A and 18B, the communication apparatus101 includes a disk-like member, and a transmission coupler 1804 and areception coupler 1808 are disposed substantially concentrically arounda point 1900. The communication apparatus 102 also includes a disk-likemember, and a transmission coupler 1810 and a reception coupler 1806 arealso disposed substantially concentrically around a point 1901. Thepoint 1900 and the point 1901 are points overlapping each other asviewed from the Z-axis positive direction of the coordinate system 200.Communication is carried out between the transmission coupler 1804 andthe reception coupler 1806, and communication is carried out between thetransmission coupler 1810 and the reception coupler 1808. Employing sucha configuration enables the communication to be carried out between thecommunication apparatus 101 and the communication apparatus 102 whileone or more of the disk-like member included in the communicationapparatus 101 and the disk-like member included in the communicationapparatus 102 is rotationally moved around an axis in the Z-axisdirection that passes through the point 1900 and the point 1901.

In the configuration example illustrated in FIGS. 18A and 18B, a groundconductor can be disposed between the transmission coupler 1804 and thereception coupler 1808 and/or the transmission coupler 1810 and thereception coupler 1806 as described with reference to FIGS. 8A and 8Bfor the purpose of preventing or reducing the interference of theelectric signal between the couplers. Alternatively, in theconfiguration example illustrated in FIGS. 18A and 18B, a shieldconductor can be provided to the communication apparatus 101 and/or thecommunication apparatus 102 as described with reference to FIGS. 13A,13B, and 13C, and 14A, 14B, and 14C for the purpose of preventing orreducing the interference of the electric signal between the couplers.

In the configuration example illustrated in FIGS. 18A and 18B, thesystem 100 can be configured such that the transmission coupler and thereception coupler supposed to communicate with each other have differentlengths from each other as described with reference to FIGS. 9A, 9B, 9C,and 9D for the purpose of preventing or reducing the interference of theelectric signal between the couplers. For example, even with thetransmission coupler 1810 shortened and shaped into an arc shape, thereception coupler 1808 with the circular shape enables the communicationto be carried out between transmission coupler 1810 and the receptioncoupler 1808 even when the coupler is rotationally moved around the Zaxis. Conversely, the transmission coupler 1810 and the receptioncoupler 1808 can have a circular shape and an arc shape, respectively.The transmission coupler 1804 and the reception coupler 1806 can havedifferent lengths from each other. In the configuration exampleillustrated in FIGS. 18A and 18B, the plurality of configurations forpreventing or reducing the interference of the electric signals betweenthe couplers can be used in combination.

<Effect of Preventing or Reducing Interference Due to Shield Conductor>

An effect of preventing or reducing the interference by the shieldconductor described with reference to FIGS. 13A, 13B, and 13C, and 14A,14B, and 14C will be described with reference to FIGS. 19A, 19B, and 19Cto FIGS. 21A, 21B, and 21C. FIGS. 19A, 19B, and 19C to FIGS. 21A, 21B,and 21C illustrate models and results of a simulation in the case wherethe rotationally movable coupler structure described with reference toFIGS. 18A and 18B is used. FIGS. 19A, 20A, and 21A are perspective viewsof models regarding the coupler portion of the communication apparatus101, and FIGS. 19B, 20B, and 21B illustrate models when the couplerportion of the communication apparatus 101 is viewed from the Z-axispositive direction. These models are constructed assuming that thecoupler is the coupler for electric field coupling that carries out thewireless communication by the differential transmission, and a conductor2000 and a conductor 2001 form the transmission coupler 1804 and aconductor 2002 and a conductor 2003 form the reception coupler 1808. Thetransmission coupler 1804 includes a power supply point P20 and thereception coupler 1808 includes a power supply point P21.

In each of the models of the simulation illustrated in FIGS. 19A, 19B,and 19C to 21A, 21B, and 21C, the transmission coupler 1804 and thereception coupler 1808 are formed as patterns on one surface (frontsurface) of a circular substrate included in the communication apparatus101. In the model of the simulation illustrated in FIGS. 20A, 20B, and20C, a shield conductor 2100 is formed as a pattern on the other surface(back surface) of the circular substrate. In the model of the simulationillustrated in FIGS. 21A, 21B, and 21C, a shield conductor 2200including a slit is formed as a pattern on the other surface (backsurface) of the circular substrate. The coupler portion of thecommunication apparatus 102 disposed to face the coupler portion of thecommunication apparatus 101 is also configured in a similar manner.

In the present simulation, the circular substrate has an outer shape of95 mm and an inner diameter of 56 mm. An outermost diameter of thecoupler (diameter of the conductor 2003) is 79 mm, and an innermostdiameter of the coupler (diameter of the conductor 2000) is 59 mm.Widths of the conductor 2000 and the conductor 2001 are each 1.5 mm, andwidths of the conductor 2002 and the conductor 2003 are each 1.0 mm. Aninterval between the conductor 2000 and the conductor 2001 and aninterval between the conductor 2002 and the conductor 2003 are each 1.5mm, and an interval between the conductor 2001 and the conductor 2002 is2.0 mm. An outermost diameter and an innermost diameter of each of theshield conductor 2100 and the shield conductor 2200 are 80 mm and 57 mm,respectively. A width and a diameter of the slit of the shield conductor2200 are 0.5 mm and 69 mm, respectively. An interval between thecircular substrate included in the communication apparatus 101 and thecircular substrate included in the communication apparatus 102 is 0.5mm.

FIGS. 19C, 20C, and 21C are graphs each indicating a simulation resultregarding a characteristic of the transmission between the couplersfacing each other in a case where the coupler portion of thecommunication apparatus 101 and the coupler portion of the communicationapparatus 102 are arranged to face each other in proximity to eachother. A vertical axis and a horizontal axis of the graph indicate again and a frequency of the transmitted electric signal, respectively. Asolid line and a dotted line in the graph indicate a characteristic ofthe transmission between the transmission coupler 1804 and the receptioncoupler 1806, and a characteristic of the transmission between thetransmission coupler 1804 and the reception coupler 1808, respectively.This graph means that a degree of preventing or reducing theinterference of the electric signal between the couplers is large if thegain of the characteristic of the transmission between the couplersadjacent to each other that is indicated by the dotted line is smallcompared to the gain of the characteristic of the transmission betweenthe couplers facing each other that is indicated by the solid line (if adifference between the gains is large).

FIGS. 19A, 19B, and 19C illustrate the model and the result of thesimulation in the case where no shield conductor is disposed. When thefrequency of the electric signal is 100 MHz, the characteristic of thetransmission between the couplers facing each other (solid line) is−12.6 dB while the characteristic of the transmission between thecouplers adjacent to each other (dotted line) is −33.4 dB, so that adifference of 20.8 dB is generated therebetween.

FIGS. 20A, 20B, and 20C illustrate the model and the result of thesimulation in the case where the shield conductor 2100 is disposed tooverlap the couplers. When the frequency of the electric signal is 100MHz, the characteristic of the transmission between the couplers facingeach other is −15.3 dB while the characteristic of the transmissionbetween the couplers adjacent to each other is −46.5 dB, so that adifference of 31.2 dB is generated therebetween. In other words, thissimulation indicates such a result that an effect of reducing theinterference by 10.4 dB can be acquired compared to the configuration inthe case where no shield conductor is used (in the case of FIGS. 19A,19B, and 19C).

FIGS. 21A, 21B, and 21C illustrate the model and the result of thesimulation in the case where the shield conductor 2200 including theslit is disposed to overlap the couplers. When the frequency of theelectric signal is 100 MHz, the characteristic of the transmissionbetween the couplers facing each other is −15.3 dB while thecharacteristic of the transmission between the couplers adjacent to eachother is −49.0 dB, so that a difference of 33.7 dB is generatedtherebetween. In other words, this simulation indicates such a resultthat an effect of further reducing the interference by 2.5 dB can beacquired compared to the configuration in the case where the shieldconductor 2100 with no slit is used (in the case of FIGS. 20A, 20B, and20C).

As described above, the wireless communication system according to thepresent exemplary embodiment (system 100, system 400, system 500, andsystem 600) includes a first antenna and a second antenna. The wirelesscommunication system includes a third antenna that carries out wirelesscommunication based on electromagnetic field coupling with the firstantenna, and a fourth antenna that carries out wireless communicationbased on electromagnetic field coupling with the second antenna. Withsuch a configuration, high-speed communication can be realized in thewireless communication system carrying out the communication based onthe electromagnetic field coupling. Disposing each of the antennas usingthe above-described various methods for preventing or reducing theinterference causes an electric signal transmitted from the firstantenna and received by the second antenna to have weaker strength thanstrength of an electric signal transmitted from the first antenna andreceived by the third antenna. In other words, the wirelesscommunication system can prevent or reduce interference of the electricsignal between the first antenna and the second antenna, andinterference of the electric signal between the third antenna and thefourth antenna.

In the present exemplary embodiment, the wireless communication systemhas been described based on the example in which the electric signal istransmitted and received between the transmission coupler and thereception coupler based on the baseband method. Based on the basebandmethod, the electric signal does not have to be modulated anddemodulated, and therefore a circuit scale can be reduced. However, thecommunication method is not limited thereto, and, for example, carriercommunication can be carried out by modulating a carrier wavetransmitted from the transmission coupler to the reception coupler basedon the electric signal generated by the transmission circuit. In thecase where the carrier communication is carried out, the interference ofthe communication can be prevented or reduced by using differentfrequencies as a frequency of a carrier wave transmitted between onepair of transmission and reception couplers and a frequency of a carrierwave transmitted between another pair of transmission and receptioncouplers.

According to the above-described exemplary embodiment, high-speedcommunication can be realized in the wireless communication system.

While exemplary embodiments have been described, it is to be understoodthat the invention is not limited to the disclosed exemplaryembodiments. The scope of the following claims is to be accorded thebroadest interpretation so as to encompass all such modifications andequivalent structures and functions.

What is claimed is:
 1. A wireless communication system comprising: afirst communication unit comprising a first antenna and a secondantenna; a second communication unit comprising a third antenna and afourth antenna; a first communication control unit configured to controlwireless data communication based on electromagnetic field couplingbetween the first antenna and the third antenna; a second communicationcontrol unit configured to control wireless data communication based onelectromagnetic field coupling between the second antenna and the fourthantenna; and a movement control unit configured to move at least one ofthe first communication unit and the second communication unitrelatively to the other while maintaining a positional relationship inwhich the first antenna faces the third antenna and the second antennafaces the fourth antenna.
 2. The wireless communication system accordingto claim 1, wherein in the positional relationship, an area of a portionof the first antenna facing the third antenna is larger than an area ofa portion of the first antenna facing the second antenna and an area ofa portion of the second antenna facing the fourth antenna is larger thanan area of a portion of the second antenna facing the first antenna. 3.The wireless communication system according to claim 1, wherein thefirst communication control unit is configured to control wirelesstransmission of a signal from the first antenna to the third antenna,and the second communication control unit is configured to controlwireless transmission of a signal from the second antenna to the fourthantenna.
 4. The wireless communication system according to claim 3,wherein a phase of a signal inputted into the first antenna issubstantially opposite to a phase of a signal inputted into the secondantenna.
 5. The wireless communication system according to claim 3,wherein the movement control unit is configured to move at least one ofthe first communication unit and the second communication unitrelatively to the other while maintaining a state in which a strength ofa signal transmitted from the first antenna to the fourth antenna isweaker than a strength of a signal transmitted from the first antenna tothe third antenna.
 6. The wireless communication system according toclaim 1, wherein the first communication control unit is configured tocontrol wireless transmission of a signal from the first antenna to thethird antenna, and the second communication control unit is configuredto control wireless transmission of a signal from the fourth antenna tothe second antenna.
 7. The wireless communication system according toclaim 6, wherein the movement control unit is configured to move atleast one of the first communication unit and the second communicationunit relatively to the other while maintaining a state in which astrength of a signal transmitted from the first antenna to the secondantenna is weaker than a strength of a signal transmitted from the firstantenna to the third antenna.
 8. The wireless communication systemaccording to claim 1, wherein the first antenna and the second antennarespectively forms shapes of lines, and the movement control unit isconfigured to move the third antenna and the fourth antenna along thelines.
 9. The wireless communication system according to claim 1,wherein the first antenna forms at least a part of a shape of a firstring, the second antenna forms at least a part of a shape of a secondring, and the movement control unit is configured to move the thirdantenna along the first ring and move the fourth antenna along thesecond ring.
 10. The wireless communication system according to claim 1,wherein the first antenna and the second antenna respectively formshapes of rings centered at a position on an axis, the third antenna andthe fourth antenna respectively form shapes of rings centered at aposition on the axis, and the movement control unit is configured torotate the third antenna and the fourth antenna around the axis.
 11. Thewireless communication system according to claim 10, wherein the firstantenna faces the third antenna in a direction of the axis, and thesecond antenna faces the fourth antenna in the direction of the axis.12. The wireless communication system according to claim 10, wherein thefirst antenna faces the third antenna in a radial direction of therings, and the second antenna faces the fourth antenna in the radialdirection of the rings.
 13. The wireless communication system accordingto claim 1, wherein the first antenna is positioned on a surface of aplate-like member, the second antenna is positioned on an oppositesurface of the plate-like member from the surface on which first antennais positioned, the third antenna is positioned on a same side from theplate-like member as the first antenna, and the fourth antenna ispositioned on a same side from the plate-like member as the secondantenna.
 14. The wireless communication system according to claim 1,wherein lengths of the first antenna and the second antenna in adirection of movement by the movement control unit are longer thanlengths of the third antenna and the fourth antenna in the direction.15. The wireless communication system according to claim 1, wherein thefirst antenna and the second antenna are positioned on a singlesubstrate, and the third antenna and the fourth antenna are positionedon another single substrate.
 16. The wireless communication systemaccording to claim 1, further comprising a conductor configured to serveas an electric ground positioned between the first antenna and thesecond antenna.
 17. The wireless communication system according to claim1, further comprising a conductor configured to serve as anelectromagnetic shield overlapping the first antenna and the secondantenna as viewed from a facing direction of antennas, wherein theconductor includes a slit at a position between the first antenna andthe second antenna as viewed from the facing direction.
 18. The wirelesscommunication system according to claim 1, further comprising a supportunit configured to support the first communication unit and the secondcommunication unit such that the movement control unit is able to movethe at least one of the first communication unit and the secondcommunication unit relatively to the other while maintaining thepositional relationship.
 19. The wireless communication system accordingto claim 1, wherein the first communication unit is comprised in a panhead portion of a camera, and the second communication unit is comprisedin an imaging portion of the camera.
 20. The wireless communicationsystem according to claim 1, wherein the first communication unit iscomprised in a hand portion of a robot arm, and the second communicationunit is comprised in an arm portion coupled with the hand portion of therobot arm.
 21. The wireless communication system according to claim 1,wherein the first communication unit is comprised in a print head of aprinter, and the second communication unit is comprised in a body of theprinter.
 22. A wireless communication system comprising: a firstcommunication unit comprising a first antenna and a second antenna; asecond communication unit comprising a third antenna and a fourthantenna; a first communication control unit configured to controlwireless transmission of a signal from the first antenna to the thirdantenna based on electromagnetic field coupling; a second communicationcontrol unit configured to control wireless transmission of a signalfrom the second antenna to the fourth antenna based on electromagneticfield coupling; and a movement control unit configured to move at leastone of the first communication unit and the second communication unitrelatively to the other while maintaining a state in which a strength ofa signal transmitted from the first antenna to the fourth antenna isweaker than a strength of a signal transmitted from the first antenna tothe third antenna.
 23. A method for wireless communication by a firstcommunication unit comprising a first antenna and a second antenna, anda second communication unit comprising a third antenna and a fourthantenna, the method comprising: controlling wireless data communicationbased on electromagnetic field coupling between the first antenna andthe third antenna; controlling wireless data communication based onelectromagnetic field coupling between the second antenna and the fourthantenna; and moving at least one of the first communication unit and thesecond communication unit relatively to the other while maintaining apositional relationship in which the first antenna faces the thirdantenna and the second antenna faces the fourth antenna.
 24. The methodaccording to claim 23, wherein in the positional relationship, an areaof a portion of the first antenna facing the third antenna is largerthan an area of a portion of the first antenna facing the second antennaand an area of a portion of the second antenna facing the fourth antennais larger than an area of a portion of the second antenna facing thefirst antenna.
 25. The method according to claim 23, wherein the movingincludes moving at least one of the first communication unit and thesecond communication unit relatively to the other while maintaining astate in which a strength of a signal transmitted from the first antennato the second antenna is weaker than a strength of a signal transmittedfrom the first antenna to the third antenna.